Rotating airfoil device



Feb. 21, 1961 w. J. SHAPIRO ROTATING AIRFOIL DEVICE 4 Sheets-Sheet 1 Filed May 22, 1956 INVE WILL/HM d. .5

P/RO

H T TOR/VEYS Feb. 21, 1961 w. J. SHAPIRO ROTATING AIRF'OIL DEVICE Filed May 22, 1956 4 Sheets-Sheet 2 INVENTOR.

l3 W/LL/HM J SHHP/Ro HTTORNEYS 1961 w. J. SHAPIRO ROTATING AIRFOIL DEVICE 4 Sheets-Sheet 3 Filed May 22, 1956 INVENTOR.

WILL/HM J. SHHPIRC Feb. 21, 1961 J SHAPIRQ 2,972,481

ROTATING AIRFOIL DEVICE Filed May 22, 1956 4 Sheets-Sheet 4 n n 52 L53 EELS T ig-.10

\ INVENTOR.

W/LL/HM J SHHP/Ro HTTORNEYS ROTATING AIRFOIL DEVICE William J. Shapiro, 658 Montgomery St., Brooklyn 25, N.Y.

Filed May 22, 1956, Set. No."586,604

8 Claims. (Cl. 273-106) The invention relates to a boomerang and propeller made of two members or blades of resilient sheet material. Cardboard is an inexpensive sheet material having sufiicient resiliency. The construction is simple yet effective to give boomerang flight or propeller rotation with out separation of the parts. The blades carry interengaging or interlocking means for retaining the blades in assembled relation and do not use any separate means to retain or secure the members of the boomerang together against separation. Various forms of construction are shown in which the blades or members of the boomerang are locked together to withstand the normal action of a boomerang so that the two parts do not separate in this normal use. The two members may be iden tical or may be different as will appear more fully hereinafter. When the two members are identical but one die is needed and but one form to be stocked and packed together.

It is an object of the invention to construct an effec tive boomerang or propeller of two members or blades of resilient material which are so constructed that they interlock without any additional means and the blades do not separate in normal use or flight and do maintain a camber.

Another object of the invention is to construct the blades or members of a boomerang or propeller having interengaging means for securing the two members together which means is such that a camber is maintained and also each member may be folded in its center for reducing its length for shipping within relatively short packages which fold will not detract from the ultimate assembly or normal operation of the boomerang or propeller.

Another object is to construct an eifective boomerang or propeller of at least one blade and of inexpensive sheet material such as cardboard, the blades of which will not separate in normal use and will maintain the camber.

Another object is to construct a boomerang or propeller which may have two, three, four or six arms with complete interengaging means embodied in the blades or members to retain them against separation and maintain the camber.

Other objects of the invention will be more apparent from the following description when taken in connection with the accompanying drawings showing preferred embodiments in which:

ates Patent boomerang which may be interlocked'together atLtheir 2,972,481 Patented'Feb. 21, 1961 centers also with the blade cambers extending in the same directions;

Figure 5 is a plan view of an assembled three-arm boomerang in which two arms extend at an angle to each other to form a unitary blade or member and the third arm is interlocked adjacent one end thereof to the center of the two-arm member;

Figure 6 is a plan view of a blade for a helicopter type of rotor or propeller, two of which are interlocked together at their centers;

Figure 7 is a plan view of a six-armed boomerang comprising two members or parts each having three equally spaced arms and which members are interlocked together at their centers to form a six-armed boomerang with each arm of one member lying between two arms of the other member;

Figure 8 is a plan view of a boomerang blade having another form of interengaging means;

Figure 9 shows a retaining memberfor maintaining the camber of a single bladed propeller or pin Wheel;

Figure 10 is a view of the operational center of a blade having recess means with the sides of the recess being at right angles to the edges of the blades; and- Figure 11 shows two blades having a different form of interengaging means. I

The boomerang as shown in Figure I may comprise two identical members or blades, each member 10 being shown as a straight strip of cardboard, although its shape may vary as desired. The blades have at least one longitudinally extending fold 11. For a boomerang having one fold this may be located centrally or spaced from the center or may extend angularly with respect to the center. Preferably, the fold is formed by slicing or cutting into the cardboard but not through the same, to form a crease in order to reduce the stiffness of the fold. The crease or fold preferably does not extend to the terminal ends of the blade or member and thereby improves the iesiliency of the fold and also improves the flight characteristic of the boomerang. member, however,.to be pressed into a V, camber form with the fold or crease 11 forming a folding axis. One or two angular folds or creases 12 and 13 may be also provided if desired extending from the end of the longitudinal crease 11 and extending to the side edges of the member so that the end of each blade or opposite ends of the member have a flat portion. For heavier cardboard, this reduces somewhat the resiliency in the fold. Also it is not necessary that both angular creases 12- and 13 be provided.

The effect of the longitudinally extending fold or folds is that each arm when the edges are squeezed together for assembly, will thereafter assume a broad V or camber as when assembling; upon release the blade will that ten to a broader V, or camber because of the resiliency in the fold and also the resiliency secured by the unfolded or uncreased terminal ends of the blade.

Interlocking means is provided at the operational center of each member or blade, the interlocking means shown in Figure 1 comprising a dove-tail recess or cutout on each edge of each member. The dove-tail in effect provides a groove for receiving the corresponding groove of the other member so that when the edges of the two members are squeezed together upon release of each'member they widen under the resiliency of the fold and the unfolded terminal ends so that the inter locking means engage to lock the members together against separation in normal use at right angles to each other. The interlocking means may be simple grooves; however, with the dove-tail form in which the opening at the edge is narrower than the bottom of the slot or cutout, the pointed projections provided by the dove-tail form engage the inclined face of the other member and It enables the blade or V =33 "assure more ettective interlocking between the members. In assembling the two members together the cambers or the points of the Vs on both members are outwardly extending or away from each other.

Figure 2 shows a construction somewhat similar to that of Figure l with the exception that instead of a centrally disposed fold or crease, each member 26 has a pair of longitudinal folds or creases 21 spaced from the edge of the member and from each other. The same interengaging means are shown for interlocking the two members together and the particular recess means disclosed at each edge of the dove-tail form. The entire edge or bottom of the dove-tail slot or cut-out should lie between the edge of the member and the crease 21 for two reasons, namely, the resiliency of the crease would be partially lost if the bottom of the slot coincided with the crease, and secondly, the edges of the other member would project beyond the face of the first member at the center.

In Figure 3 the construction of the member is similar to that shown in Figure l but with a difierent interengaging construction at the centers of the members. In this construction the interengaging means is different on one blade from that on the other. One member 24 has a slot or recess 25 extending from each edge thereof and at the operational center of the member. The other member 26 has a pair of spaced recess means 29 which means are joined to form a central aperture into which extends a projection 27. These projections are in alignment with the crease llll; that is, each projection extends towards the opposite end of the blade with a groove formed between the projection and the edge 29 of the aperture. The edges of the recess means preferably are angular with respect to each other. These two blades or members are assembled together so that the projections 27 are received in the slots 25 with the camber or the V extending in the same direction. The edges of the projection engage the edges of the slot to retain the two members at right angles to each other. The resiliency of the member 24 tends to straighten the V and thereby firmly projects the slot 25 into th engagement with the projections 27 and by a like token the resiliency of the member 26 to straighten somewhat grips the member 24 in the grooves on each side of two projections.

Figure 4 shows a construction in which the member 32 is identical with that shown in Figure 1. The cooperating "member 33, however, has a slightly different form of slot or cut-out in that it does not have a fiat bottom. The bottom has two angularly displaced sides 34. The reason for the angularly displaced sides of the bottom is that this boo'merange is designed to have the camber or V extending in the same direction for both members. In other words, the V sides 34 of the cut-out provide clearance for the V form of the member 32 when interlocked together in their recesses. The two members are interlocked together in essentially the same manner as the boomerang of Figure l with the resiliency of the members at the crease expanding at the edges thereof 'so that the interlocking means grip and interlock the two members together at right angles to each other.

Figure illustrates a boomerang having three arms in that one member 3'7 has a pair of arms extending at an angle of 120 with respect to each other. Each arm has a fold or crease ii shown as centrally located. The interengaging means is the dove-tail form of recess means 16 as shown in Figure 1, and in the member 32'. of Figure 4 located at its operational center and in each edge of the blade. The other member or blade 38 is a single blade arm with recess means at each edge and at its operational center which is adjacent the inner end of the arm. The recess means of each blade are interengaged by pressing the edges of a blade together to interlock the recesses of the double armed member 37 with the single armed member to form three arms spaced 120 apart.

Figure 6 shows a member or blade 41 which operates as a propeller, helicopter rotor, or pin wheel. The crease or told 11 does not extend along the central axis between the edges of the arms or members and preferably extends parallel with one of the edges. This makes a blade having a wider trailing portion and a narrower leading portion of a propeller blade, a helicopter blade or pin wheel. A recess means 16 is provided at each edge at the open ational center. Two such blades are assembled by interengaging the interlocking recess means llii. Two such identical blades or members when assembled together with their cambers extending in opposite directions provide a structure in which the trailing edge portions are adjacent to each other in two opposite quadrants and the leading edge portions of the two blades are adjacent in the other two opposite quadrants. A hole $3 is provided in each member to receive a propeller shaft such as a nail or pin. The propeller will function as a helicopter rotor it thrown upwardly or allowed to drop from a height.

Figure 7 shows a construction of boomerang having six-arms in which each member as, :7 as three arms equally disposed apart. Each is provided with an interengaging recess means between each arm and hence at each edge, there being three edges with this form. The recess means may be of the dovetail form 16 illustrated with respect to the two-member boom'erangs. Two such identical three-arm members are assembled together with the cambers extending in opposite directions and so that each arm of one member is located between a pair of arms of the other member. Y I

Figure 8 illustrates another form of blade or member 59 having a fold or crease 51. In this blade the recess means is a pair of spaced notches 52 and 53 on each edge thereof at the operational center of the blade. These notches are relatively narrow although wider than tle thickness of the cardboard. Two of these blades are assembled together at right angles to each other by bending or flexing the edges towards each other narrowing the V of the camber and interengaging the notches or recess means at each edge of a like blade whereupon release of the edges spreads the V of the camber and retains the two blades together. The resiliency of the blade at the fold or crease presses the edges of the notch of the two blades together to retain the interlock against separation, and also retains the camber against flattening out. This is accomplished by spacing the pair of notches 52 and 53 a distance apart less than the open .I spacing between the notches on opposite edges so that the camber is positively maintained when the two blades are assembled together. Also the resiliency of the fold aids in retaining the blades against separation in use and secures a clamping action between the blades in the notch as will appear hereinafter.

Figure 9 shows a cooperating member which serves as a retaining member only. It may be used with a single blade as shown in Figure 6 to retain the camber of the blade or member. This produces a single blade propeller or pin wheel which will rotate on the center 43 when moved to create a wind stream past the blade.

Figure 10 shows the operational center of a blade or member 56 having a longitudinal fold 11 as described in connection with the other figures. At each edge of the blade is a straight-sided recess forming the interengaging means with an identical second blade. The spacing between the lateral edges 59 is spaced apart less than the width at the bottom of the recess of the blade in open V condition and sufiiciently less so that the resiliency of the fold exerts pressure outwardly against the interengaging recesses'on two assembled blades. In this construction it is primarily the resiliency of the blades at the fold pressing the edges outwardly which retains the blades in interengaging relation against separation in boomerang or propeller use.

Figure 11 is another form in which the interengaging means includes recess means in one member and cooperating means on the other member. The recess means is carried by one member or blade 60 only. The recess means is each of a pair of spaced slots 61 and 62 one on each side of the fold 11. The slots are V-shaped with the point of the V preferably facing the edge of the blade to secure opposed cambers. The V form is used in order to maintain the camber of the other blade which is received in the slots. The other member 63 has straight edges with a stop or projection 64 extending outwardly from each edge. These edges at the operational center and the projections constitute cooperating means of the interengaging means. The two members are assembled by squeezing the edges together and inserting the terminal end through the recess until the projections are engaged. The slots have a dimension for the length of the V corresponding to the width between the edges of the other member. The V slots, however, are narrow so that when the camber or V is narrowed by squeezing the edges, the other blade passes easily therethrough. When the edge pressure on the blade is released and the V widens under the resiliency of the blade or fold, this changes the angular relation of the slot with respect to the blade received therein and has the effect of narrowing the slot with respect to the thickness of the blade and thereby grips or clamps the blades against separation in normal use,

It has been mentioned that the longitudinal fold or crease has resiliency. That is, when the edges of a blade are pressed together the blade will assume a fixed or natural camber or V, when the pressure is released. The V is an open V. With any subsequent pressing of the edges of the blade together into a sharper V or camber, the resiliency of the blade or fold restores the blade to its open V or camber which factor aids in retaining the blades in assembled relation as will appear.

In the various forms of interengaging or interlocking means illustrated there is recess means carried by one member and cooperating means carried by the other. In most of the forms illustrated the cooperating means is also a recess means. The recess or interengaging means may be in the edge of the bladeor adjacent to the edge, that is in the region of the edge. There may be one or more of three factors used to retain the blades into interengaging relation against separation. In the form shown in Figure l, the recess means is a dove-tail recess in each edge so that the dove-tail forms a groove. A groove alone may retain the two blades in interlocked relation without using the resiliency of the fold or crease or the overall resiliency of the blade to press the edges of the recess outwardly and use this additional structure and characteristic to retain the blades against separation. In the former construction the spacing between the bottoms of the grooves or notches is the same as or somewhat greater than the spacing between the bottoms of the recess means of the other blade in open V or camber so that the resiliency of the fold is not a factor in retaining the blades against separation. It is solely the interengaging notches or grooves that would perform this function. In order to maintain the camber, the spacing discussed should not be greater than the lateral spacing between the two interengaging means of the other member. When this spacing is equal there is enough interference between edges to maintain some camber. Preferably, the spacing between the opposite grooves or sides of at least one recess means is less than the lateral distance between the two recess means on the other member when in expanded or open position of the camber or V so that when released the resiliency of the fold or crease or the resiliency of the blade presses the recesses or the edges of the recesses of the two blades together so that it is both the groove formation and the resiliency of the fold or blade pressing the interengaging means together which cooperates to retain the two blades against separation.

There is also a clamping or gripping actionto aid in retaining the blades together which is more particularly 8. exemplified in the construction of Figures 8 and llfor aid in retaining the interengaging means against separation. In other words, the spaced slots 52 and 53 forming the recess means are narrow so that when the edges of the blade are pressed together to form a sharper V, the recesses are interengaged easily. When the edges are released so that the resiliency of the fold or member widens or opens the 'V or camber, the angle of the blade portion received in the narrow slot changes with respect to the slot so that the surfaces passing through the slot are clamped or gripped between opposite edges of the slot. 1 That is, the effect of opening or spreading of the camber has the effect of narrowing the slot with respect to the thickness of the material by changing the relative angle between the portion of the blade received in the slot and the slot in this manner grips or clamps the interengaging means or blades together against separation. In Figure 10 as previously discussed, it is primarily the resiliency of the fold or blade in broadening or opening the V which presses the interengaging means in interengaging or interlocking relation to prevent separation of the two blades forming the boomerang or propeller.

- In all constructions an additional function of the interengaging means is to retain the camber in each blade of the boomerang. It will be observed, too, that in all constructions of the boomerang or propeller the interengaging means secures the blades together without any additional means not a part of the blades such as an elastic, staple, clip, rivet, center pivot, and the like, which are common expedients in retaining boomerang blades together. Also with the interengaging means, the blades may be folded on a central lateral axis thereby reducing their packaging length so that they may be packed in a relatively small package; The interengagingmeans and the camber when the blades are assembled stiffen this fold so that it does not affect the assembled blades. The camber either in folded or curved form of the blade also gives longitudinal stifiness to the member or blade as well as stiifness at a lateral mid-fold if used.

The blades or members are of resilient sheet material. Cardboard is particularly suitable because of its low cost and when folded or creased has adequate resiliency at the fold. Resilient blades of metal, plastic or the like, would not need a fold or crease since the overall resiliency would sufiice. Cardboard having a thickness as light as about 14 points and heavier is suitable. As a general rule, the longer the blades, the heavier the cardboard to be used to give sufficient stifiness. The effective boomerangs and propellers have been constructed of cardboard of 25 and 30 point thickness, with blades having a length of about 12 inches and of l8'point thickness with a blade length of about 8 inches. Propellers or pin wheels of a blade length of about two inches could use a thickness of cardboard of about 4 points or heavier.

The blades may be printed as blanks on cardboard and left to children to cut out and assemble. The cardboard material in which food products are packaged provides a suitable cardboard. In this event, the longitudinally extending fold or crease, constitutes a folding axis as a direction to the maker to fold and/or crease at this axis.

This invention is presented to fill a need for improvements in a boomerang and propeller. It is understood that various modifications in structure, as. well as changes in mode of operation, assembly and manner of use, may and often do occur to those skilled in the art, especially after benefiting from the teachings of an invention. Hence, it will be understood that this disclosure is illustrative of preferred means of embodying the invention in useful form by explaining the construction, operation and advantages thereof.

What is claimed is:

1. A device of the character described comprising a member of cardboard having at least two arms, each arm having a length greater than its width, at cooperating member, each member having at least one terminal end and an -operational center and an edge on each side, at least one told extending longitudinally of each member forming angular portions, and interengaging means carried by each member at its operational center including a pair of spaced recess means carried by one of the mem .bers at each edge thereof, and a cooperating means on the cooperating member receiving the recess means of the first member when extending at an angle with respect thereto to retain the two members in assembled relation, each recess means having a dimension in a longitudinal direction no greater than the spacing between the cooperating means on the other member to retain the two members in assembled relation and camber form, and in which the fold ends at a distance from each terminal end.

2. A device of the character described as in claim 1 including at least one fold extending from the end of the longitudinally extending fold to the edge of the member.

3. A device of the character described comprising a member of cardboard having at least two arms, each arm having a length greater than its width, a cooperating member, each member having at least one terminal end and an operational center and an edge on each side, at least one fold extending longitudinally of each member forming angular portions, and interengaging means carried by each member at its operational center including a pair of spaced recess means carried by one of the members at each edge thereof, and a cooperating means on the cooperating member receiving the recess means of the first member when extending at an angle with respect thereto to retain the two members in assembled relation, each recess means having a dimension in a longitudinal direction no greater than the spacing between the cooperating means on the other member to retain the two members in assembled relation and camber form, and in which each member has three arms extending at an angle of 120 with respect to its adjacent arms.

4. A pair of blade blanks for a rotatingairfoil device comprising a first member of resilient material having at least two arms and each arm having a length greater than its width, the member having an operational center with at least two opposite edges, each arm having a terminal end, each arm having the same width and the same length from the operational center, at least one bending axis extending longitudinally of at least the operational center of the member for forming angularly directed portions, a cooperating member having at least an operational center and having oposite edges at the operational center, and interengaging means carried by each member at its operational center including recess means carried by said first member in the region of each edge thereof and spaced from each other, and a cooperating means on the cooperating member on opposite edges thereof receiving the recess means of the first member when extending at an angle with respect thereto to retain the two members in assembledrelation, each recess means having a dimension in a longitudinal direction to .give solely a rotating aerodynamic lift characteristic with respect to an edge along at least a major length of a longitudinal axis extending from the center of the operational center of the first member and an equal lift characteristic to the cooperating member along its longitudinal central axis when the two members are assembled together, said longitudinal dimension of each said recess means having a maximum value no greater than that of the lateral spacing between the cooperating means on the other memher, said longitudinal dimension of each said recess means and the cooperating means having a minimum value no less than that which is sutficient only to impart said aero: dynamic lift characteristic to said first member and the cooperating member, the lateral spacing between the ends of the recess means being the same, and the lateral spacing between the ends of the cooperating means being the same and the same as that of the recess means, and the recess means and the cooperating means retaining the two members in assembled relation.

5. A pair of blade blanks as in claim 4,in which the recess means extends inwardly from each edge of the member.

6. A pair of blade blanks as in claim 4 in which the recess means is spaced from the edges of the member.

7. A pair of blade blanks as in claim 4 in which the blade blanks are identical, and the recess means and the cooperating means extend inwardly from each'edge of its member.

8. A pair of blade blanks as in claim 7 in which the cooperating means at each edge has a longitudinal dimension no greater than the lateral spacing between the two recess-means of the other member.

References Cited in the file of this patent UNITED STATES PATENTS 

